Auto-router performing simultaneous placement of signal and return paths

Abstract

An auto routing method and system provides optimized circuit routing while maintaining proper reference return paths for critical signals. Critical signal paths are auto-routed simultaneously with corresponding reference return paths, and the reference return paths can be merged into reference planes if they are adjacent to regions connected to the same reference net. The reference return paths may be in a plane adjacent to the signal path plane in the same channel, or the reference returns may be routed in adjacent channels in the same plane as the signal path. A check may be performed on endpoints of each critical signal path to determine whether a reference return via is present within a proximity tolerance of the signal path endpoints, and a reference return via placed if not.

1. A computer-performed method of designing an electrical circuit interconnect structure, comprising:
 in a computer model of an interconnect structure design, routing, using a computer, a first conductive path for a critical signal using auto-routing algorithm; 
 prior to accepting the first conductive signal path as a routed path according to an auto-routing path acceptance criteria, routing a second conductive path for a reference return corresponding to the critical signal proximate the first conductive path, wherein the auto-routing path acceptance criteria requires meeting criteria for placement of both the signal path and the reference return path; 
 responsive to meeting the auto-routing path acceptance criteria for both of the first conductive path and the second conductive path, accepting the first conductive path and the second conductive path as a routed pair for the critical signal and the corresponding reference return; 
 responsive to not meeting the auto-routing path acceptance criteria for either of the first conductive path or the second conductive path, repeating the routing of the first conductive signal path using another routing and repeating the routing of the second conductive signal path; and 
 repeating the routing a first conductive path, routing a second conductive path and accepting for other critical signals. 
 
     
     
       2. The computer-performed method of  claim 1 , wherein the routing a first conductive path and the routing a second conductive path route the first conducive path and the second conductive path in parallel channels of the same layer of the interconnect structure. 
     
     
       3. The computer-performed method of  claim 1 , wherein the routing a first conductive path and the routing a second conductive path route the first conducive path and the second conductive path in substantially identical channels of adjacent layers of the interconnect structure. 
     
     
       4. The computer-performed method of  claim 1 , further comprising checking the second conductive path for return vias proximate endpoints of the first conductive path, and wherein in response to the checking determining that a return via is not within an allowable distance from an endpoint of the first conductive path, placing a return via within the allowable distance. 
     
     
       5. The computer-performed method of  claim 1 , further comprising determining whether or not the second conductive path is adjacent to another conductive region connected to a plane connected to the same net as the reference return, and if the second conductive path is adjacent to another conductive region connected to a plane corresponding to the reference return, merging the second conductive path with the another conductive region. 
     
     
       6. The computer performed method of  claim 5 , wherein the auto-routing algorithm uses a criterion for causing the second conductive path to be preferably placed adjacent to other reference paths having the same net, whereby contiguous reference planes are preferred. 
     
     
       7. The computer-performed method of  claim 6 , further comprising checking the second conductive path for return vias proximate endpoints of the first conductive path, and wherein in response to the checking determining that a return via is not within an allowable distance from an endpoint of the first conductive path, placing a return via within the allowable distance. 
     
     
       8. A computer program product comprising a non-transitory computer-readable storage media containing program instructions for execution by a processor for designing an electrical circuit interconnect structure, the program instructions comprising program instructions for:
 in a computer model of an interconnect structure design, routing a first conductive path for a critical signal using auto-routing algorithm; 
 prior to accepting the first conductive signal path as a routed path according to an auto-routing path acceptance criteria, routing a second conductive path for a reference return corresponding to the critical signal proximate the first conductive path, wherein the auto-routing path acceptance criteria requires meeting criteria for placement of both the signal path and the reference return path; 
 responsive to meeting the auto-routing path acceptance criteria for both of the first conductive path and the second conductive path, accepting the first conductive path and the second conductive path as a routed pair for the critical signal and the corresponding reference return; 
 responsive to not meeting the auto-routing path acceptance criteria for either of the first conductive path or the second conductive path, repeating the routing of the first conductive signal path using another routing and repeating the routing of the second conductive signal path; and 
 repeating the routing a first conductive path, routing a second conductive path and accepting for other critical signals. 
 
     
     
       9. The computer program product of  claim 8 , wherein the program instructions for routing a first conductive path and the program instructions for routing a second conductive path route the first conducive path and the second conductive path in parallel channels of the same layer of the interconnect structure. 
     
     
       10. The computer program product of  claim 8 , wherein the program instructions for routing a first conductive path and the program instructions for routing a second conductive path route the first conducive path and the second conductive path in substantially identical channels of adjacent layers of the interconnect structure. 
     
     
       11. The computer program product of  claim 8 , further comprising program instructions for checking the second conductive path for return vias proximate endpoints of the first conductive path, and wherein in response to the checking determining that a return via is not within an allowable distance from an endpoint of the first conductive path, placing a return via within the allowable distance. 
     
     
       12. The computer program product of  claim 8 , further comprising program instructions for determining whether or not the second conductive path is adjacent to another conductive region connected to a plane connected to the same net as the reference return, and if the second conductive path is adjacent to another conductive region connected to a plane corresponding to the reference return, merging the second conductive path with the another conductive region. 
     
     
       13. The computer program product of  claim 12 , wherein the auto-routing algorithm uses a criterion for causing the second conductive path to be preferably placed adjacent to other reference paths having the same net, whereby contiguous reference planes are preferred. 
     
     
       14. The computer program product of  claim 13 , further comprising program instructions for checking the second conductive path for return vias proximate endpoints of the first conductive path, and wherein in response to the checking determining that a return via is not within an allowable distance from an endpoint of the first conductive path, placing a return via within the allowable distance. 
     
     
       15. A workstation computer system, comprising a processor for executing program instructions and a memory for storing the program instructions and data, wherein the program instructions include program instructions for designing an electrical circuit interconnect structure, the program instructions comprising program instructions for:
 in a computer model of an interconnect structure design, routing a first conductive path for a critical signal using auto-routing algorithm; 
 prior to accepting the first conductive signal path as a routed path according to an auto-routing path acceptance criteria, routing a second conductive path for a reference return corresponding to the critical signal proximate the first conductive path, wherein the auto-routing path acceptance criteria requires meeting criteria for placement of both the signal path and the reference return path; 
 responsive to meeting the auto-routing path acceptance criteria for both of the first conductive path and the second conductive path, accepting the first conductive path and the second conductive path as a routed pair for the critical signal and the corresponding reference return; 
 responsive to not meeting the auto-routing path acceptance criteria for either of the first conductive path or the second conductive path, repeating the routing of the first conductive signal path using another routing and repeating the routing of the second conductive signal path; and 
 repeating the routing a first conductive path, routing a second conductive path and accepting for other critical signals. 
 
     
     
       16. The workstation computer system of  claim 15 , wherein the program instructions for routing a first conductive path and the program instructions for routing a second conductive path route the first conducive path and the second conductive path in parallel channels of the same layer of the interconnect structure. 
     
     
       17. The workstation computer system of  claim 15 , wherein the program instructions for routing a first conductive path and the program instructions for routing a second conductive path route the first conducive path and the second conductive path in substantially identical channels of adjacent layers of the interconnect structure. 
     
     
       18. The workstation computer system of  claim 15 , further comprising program instructions for checking the second conductive path for return vias proximate endpoints of the first conductive path, and wherein in response to the checking determining that a return via is not within an allowable distance from an endpoint of the first conductive path, placing a return via within the allowable distance. 
     
     
       19. The workstation computer system of  claim 15 , further comprising program instructions for determining whether or not the second conductive path is adjacent to another conductive region connected to a plane connected to the same net as the reference return, and if the second conductive path is adjacent to another conductive region connected to a plane corresponding to the reference return, merging the second conductive path with the another conductive region. 
     
     
       20. The workstation computer system of  claim 19 , wherein the auto-routing algorithm uses a criterion for causing the second conductive path to be preferably placed adjacent to other reference paths having the same net, whereby contiguous reference planes are preferred.